The present invention relates generally to oil condition sensors.
A major threat to vehicle engine oil is antifreeze leaking into the oil system from the coolant system. Antifreeze in concentrations as low as a few hundred parts-per-million (ppm) can cause detrimental changes in the engine oil. For example, sludge deposits can form at the location where the antifreeze leaks into the oil. Moreover, the antifreeze in the oil can react with anti-wear additives, e.g., zinc alkyldithiophosphate (ZDP). If a significant amount of ZDP is affected, anti-wear protection may be lost, and catastrophic camshaft and valve lifter wear will result. Also, the loss of the ZDP could hasten the degradation of the engine oil.
Under normal operating conditions, small amounts of antifreeze leaking into the engine oil is dispersed by dispersants and detergents in the engine oil. After dispersal, the adverse effects of antifreeze on the engine components and engine oil would be reduced considerably. However, continuous antifreeze leakage would eventually deplete all of the dispersants, and any undispersed antifreeze can cause the problems mentioned above.
Current sensors exist which detect undispersed antifreeze in engine oil. Since undispersed antifreeze does not mix with the engine oil, but rather settles at the bottom of the oil pan, it can be detected by an engine oil condition sensor located at the bottom of the pan. These sensors, however, do not detect dispersed antifreeze. Consequently, until all of the dispersants are depleted and undispersed antifreeze begins to collect in the bottom of the oil pan, the driver is unaware of an antifreeze leak into the engine oil and is unable to have the leak repaired before damage to the engine occurs.
The present invention has recognized these prior art drawbacks, and has provided the below-disclosed solutions to one or more of the prior art deficiencies.
A method for determining dispersed antifreeze contamination of oil within an engine using an oil contamination sensor includes starting the engine and heating the oil. The output voltage of the sensor is measured and based on the output voltage of the sensor, it is determined whether antifreeze is being dispersed in the oil.
In one aspect of the present invention, the oil has a relatively rapid resistance change over the life of the oil and the method includes heating the oil to a low temperature range and measuring a series of output voltages from the sensor. The present output voltage is compared to an immediately previous voltage value and based on this comparison, it is determined whether antifreeze is being dispersed in the engine oil. In this aspect, the low temperature range is from thirty degrees Celsius to forty degrees Celsius (30xc2x0-40xc2x0).
In another aspect of the present invention, the oil has a relatively slow resistance change over the life of the oil, and the method includes heating the oil to a predetermined middle temperature range and determining a threshold voltage value, Vth. A first difference value, DV1, a second difference value, DV2, and a third difference value, DV3, are determined. These difference values, DV1, DV2, DV3, are compared to the threshold voltage value, Vth. Based on the comparison, it is determined whether antifreeze is being dispersed in the engine oil. In this aspect, Vth=A*Vref, where A is a percentage value. Also, Vref=(Vnxe2x88x925+Vnxe2x88x924+Vnxe2x88x923)/3, where Vref=a starting reference voltage, Vnxe2x88x925=a fifth previous voltage value, Vnxe2x88x924=a fourth previous voltage value, Vnxe2x88x923=a third previous voltage value. Moreover, DV1=abs (Vnxe2x88x922xe2x88x92Vref), DV2=abs (Vnxe2x88x921xe2x88x92Vref), and DV3=abs (Vnxe2x88x92Vref), where Vnxe2x88x922=a second previous voltage value, Vnxe2x88x921=a first previous voltage value, and Vn=a current voltage value. A is from ten percent to fifteen percent (10%-15%).
In this aspect of the present invention, the method also includes determining whether any two of the three difference values, DV1, DV2, DV3, are greater than the threshold value, Vth. Based on this determination, it is indicated whether antifreeze is dispersed in the engine oil. In this aspect, the middle temperature range is from forty degrees Celsius to sixty degrees Celsius (40xc2x0-60xc2x0).
In yet another aspect of the present invention, an oil contamination sensor includes a first sensing electrode and a second sensing electrode. A sensing area is established between the electrodes and the sensing area is submerged in engine oil. This aspect of the present invention also includes a microprocessor connected to the sensing electrodes. The microprocessor includes a program for determining whether antifreeze is dispersed in the engine oil.
The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: